Frieden told reporters that not all of the increases came in the last month of the pandemic, since the model used to make the calculations takes into account such issues as late reporting.

"But there has been a lot more disease in the month that's reported than in the month before," he said.

The pandemic continues to disproportionately affect younger people, Frieden said, noting that 1,100 children have died, along with 7,500 "younger adults," many of them under 50.

The H1N1 pandemic strain is still the main cause of influenza, he said, although experts are now beginning to see some cases caused by the seasonal flu, influenza B. The strain involved matches the seasonal flu vaccine for this year, Frieden said.

Frieden added that about 85 million doses of the H1N1 vaccine are now either available or have been distributed. In many places, the vaccine is now available to the general public.

He said the agency's polling is "quite consistent -- about half of Americans want to and plan to be vaccinated."

"This is a great window of opportunity for people who have been waiting for their turn," he said.

Frieden added that even though the disease seems to be declining, it's too early to say the pandemic is over.

"We don't know what the future will hold," he said. "We're at the beginning of December and the flu season lasts until May."